Definition of Metaphor
Throughout American Dirt, Cummins uses a metaphor to compare the migrants' train to a beast. The train is colloquially known as "La Bestia," but Cummins occasionally refers to it simply as "the beast." In Chapter 20, she writes:
They cheer when they see the train approaching, but the beast doesn’t slow, it’s moving too fast for them to board, so the men stand despondent, watching it thunder past.
In order to travel toward the United States, the migrants jump onto La Bestia and ride on top—the train doesn't stop. This is a dangerous operation, and Lydia is terrified to attempt it with Luca.
By calling the train simply "the beast," Cummins writes about the train as if it were a true animal rather than a locomotive named after an animal. This comparison suggests that the train has a mind of its own and moves on its own accord, not taking the migrants into account. The particular comparison to a "beast," rather than any animal, reinforces the fact that the train is formidable and a true threat to the migrants. This danger is emphasized when Lydia and Luca watch a man fall off and die as he attempts to jump onto La Bestia. The threat of the train shows how dangerous every element of the migrants' travel is.